ANCIENT CRYSTALLINE ROCKS-GRANITE. 
45 
The chemical character of this type of granite is expressed in the following 
analyses, made by Doctor Hillebrand: 
Analyses of Pikes Peak granite. 
! i. 
II. 
! 1 . 
II. 
77.03 
66.20 
so 3 . 
None. 
M 203 . 
12.00 
14.33 
Cl. 
Trace. 
.76 
2.09 
F. 
.36 
(?) 
FeO. 
.86 
1.93 
.12 
MsO. 
.04 
.89 
MnO. 
Trace. 
.13 
CaO. 
.80 
1.39 
BaO. 
Trace. 
.18 
Na s O. 
3.21 
2.58 
SrO. 
None. 
Trace. 
K,0... 
4.92 
7.31 
Li 2 0. 
Trace. 
Trace. 
II 2 0-..'. 
.14 
.48 
H 2 0+. 
.30 
.83 
100.55 
99.74 
TiO •>...'. 
.13 
.65 
Less O for F. 
.15 
0. 
Zr0 2 . 
.02 
100.40 
99.74 
C0 2 . 
.36 
PjOi. 
Trace. 
.25 
I. Pikes Peak granite. Typical. Sentinel Point, western part of Pikes Peak massif. Jour. Geol., vol. 8, 1900, p. 237. 
II Pikes Peak granite. Local syenitic facies. Ajax mine, level 6. 
\ 
CRIPPLE CREEK GRANITE. 
Extending from the volcanic area westward beyond the mapped district is a 
light-red granite, which differs in texture from the Pikes Peak type and which has 
received the name Cripple Creek type. It is a medium, fairly even-grained rock, 
with an occasional feldspar (larger and more idiomorphic than the rest, causing a 
slight porphyritic appearance. Quartz is somewhat more abundant and more 
evenly distributed than in the Pikes Peak granite, and the same may be said ol 
mica. To this type is assigned the island-like mass of granite in the breccia on Bull 
and Ironclad hills. 
Concerning the correlation of the dikes and irregular masses of finer grained 
granite found cutting the Pikes Peak granite, there may be some doubt. Mathews 
refers some of them to the Cripple Creek type and some to a separate division which 
he calls the “fine-grained type.” But from such evidence as could be obtained 
both in the field and with the microscope, the smaller areas appear to be composed 
of a rock which corresponds closely with the Cripple Creek variety, and where it was 
possible to define their boundaries, they have been mapped as such. It is not 
unnatural that the smaller masses should in general have a finer grain than the 
large areas. The Cripple Creek granite has suffered much less shearing and deforma¬ 
tion than the Pikes Peak type. 
The results of the weathering of this rock contrast in some respects with those 
produced by that of the coarser grained variety. Instead of crumbling to angular 
gravel, this granite yields on disintegration subangular blocks of large and small 
size. This probably accounts for the apparent abundance of the dike granite in 
the Pikes Peak variety, fragments of the finer grained rock littering the surface of 
the coarser grained rock. On this account also the mode of alteration of the 
13001 — No. 54—06 - 5 
